Rubbing seal for a rotary regenerative heat exchanger

ABSTRACT

A rubbing seal for engagement with a hot face of a matrix of a rotary regenerative heat exchanger. The seal comprises a ferritic steel base member, a rubbing surface layer including nickel oxide and an intermediate bonding layer of a nickel aluminum compound between the base member and the rubbing surface layer.

States Patent [1 1 Silverstone et al.

RUBBING SEAL FOR A ROTARY REGENERATIVE HEAT EXCHANGER Inventors: CalvinEric Silverstone; Alan John Surrall, both of Solihull, England Assignee:Leyland Gas Turbines Limited,

Solihull, England Filed: June 1, 1971 Appl. No.: 148,529

Foreign Application Priority Data June 26, 1970 Great Britain.,3l,069/7() US. Cl ..277/96 R, 106/63, 165/9, 7 277/DIG. 6

Int. Cl. ..Fl6j 15/16 Field of Search ..l65/9; 277/96 R,

277/DIG. 6; 106/39 R, 55, 63

[ 51 May 1, 1973 [56] References Cited UNITED STATES PATENTS 3,646,9933/ l 972 Rice et al. 165/9 3,204,969 9/1965 Williams ...l65/9 X3,351,]27 l 1/1967 Mendelsohn 165/9 3,633,926 l/l972 Hryniszak et a1. I65/9 X Primary Examiner-Albert W. Davis, Jr. Attorney-Mawhinney &Mawhinney [5 7] ABSTRACT A rubbing seal for engagement with a hot faceof a matrix of a rotary regenerative heat exchanger. The seal comprisesa ferritic steel base member, a rubbing surface layer including nickeloxide and an intermediate bonding layer of a nickel aluminum compoundbetween the base member and the rubbing surface layer.

2 Claims, 1 Drawing Figure PATENTEU-WH!175 $730,538

INVENTORS CALVIN Ema SlLvEESTNE JOHN SUZRALL The invention relates to arubbing seal for a rotary regenerativeheat exchanger and is particularlyconcerned with a rubbing seal for engagement with a hot face of thematrix of a rotary regenerative heat exchanger for a gas turbine engine.

Existing rubbing seals for engagement with a hot face of the matrix of arotary regenerative heat exchanger have been formed by depositing alayer containing nickel oxide and calcium flouride on to an austeniticstainless steel base member. Such a seal has suffered from thedisadvantage that at high engine operating temperatures, the depositedlayer has become detached from the base member. The reason for this isbelieved to be that there is a difference between the expansionco-efficient of stainless steel and that of nickel oxide, theapproximate expansion co-efficient of stainless steel being 18 X l /Cand that of nickel oxide being 13 X lO /C. An object of this inventionis to provide a rubbing seal in which the co-efficients of expansion ofthe material of the base member and of the actual seal material aresubstantially the same.

Another disadvantage of the existing seal is that the seal materialcontains calcium fluoride, thereby giving rise to a health hazard.Therefore another object of the invention is to avoid the use of calciumfluoride in the rubbing seal material.

According to the invention a rubbing seal, for engagement with a hotface of a matrix of a rotary regenerative heat exchanger, comprises aferritic steel base member and a rubbing surface layer including nickeloxide.

The seal may include an intermediate bonding layer of a nickel aluminumcompound. A suitable material is available commercially as Metco 405, amaterial manufactured by Metco Limited.

The rubbing surface layer may be formed from a powder comprising amixture of nickel oxide and calcium carbonate, the quantitiy of thelatter by weight being not more than percent of the total composition ofthe powder. Alternatively the powder may comprise a mixture of nickeloxide, metallic nickel and calcium carbonate, the quantity of nickel andclacium carbonate by weight being not more than 25 percent and 10percent respectively of the total composition of the powder.

By way of example, a rubbing seal in accordance with the inventioncomprises a base member of a ferritic steel, instead of using anaustenitic stainless steel as hitherto. The ferritic steel base membermaybe protected against oxidation by depositing on it a bonding layer ofa nickel aluminum compound, for example, that known as Metco 405. Thedeposition of the compound is conveniently efiected by a flame gun. Arubbing seal layer is formed on the bonding layer or, where a bondinglayer is not required, directly on to the fern'tic steel base member, bydepositing with a flame gun a powder containing nickel oxide. The powderemployed may either be a mixture of nickel oxide and calcium carbonate,the quantity of the latter by weight being not more than 10 percent or amixture of nickel oxide, metallic nickel and calcium carbonate, thequantities of nickel and calcium carbonate by weight being not more than25 percent and 10 percent respectively.

A section through a typical rubbing seal in accordance with theforegoing example is illustrated in the accompanying drawing. Thesealcomprises a ferritic steel base member 1 attached, by welding, brazingor otherwise, to a metal bellows 2. The bonding layer of the nickelaluminum compound, e.g., Metco 405, is

shown at 3. This, as aforesaid, is conveniently deposited on the basemember by using a flame gun. The actual rubbing seal material which isdeposited on to the bonding layer 3 by flame deposition is shown at Thewear rate of the layer formed by flame deposition of nickel oxide andcalcium carbonate is similar to that produced from a nickel oxide andcalcium fluoride mix, but the wear rate of the alternative mixture ofnickel oxide, metallic nickel and calcium carbonate has approximatelyten times less wear rate than the known rubbing seal composition usingnickel oxide and calcium fluoride. It is believed that the reason forthis significant improvement in wear rate lies in the higher density ofthe deposit resulting from the in situ oxidation of the nickel in thepowder mixture.

In either case the powder mixture has an expansion co-efficient similarto that of the ferritic steel base of approximately 13 X l0 /C.

The powder mixtures proposed herein are cheaper to produce than mixturesused at present as they do not include calcium fluoride and furthermorethe health hazard arising from calcium fluoride is not present.

What we claim as our invention and desire to secure by Letters Patent ofthe United States is:

l. A rubbing seal for engagement with a hot face of a matrix of a rotaryregenerative heat exchanger, the seal comprising a ferritic steel basemember and a rubbing surface layer formed from a powder comprising amixture of nickel oxide, metallic nickel and calcium carbonate, themaximum quantity of nickel and calcium carbonate by weight being 25percent and 10 percent respectively of the total composition of thepowder.

2. A seal as claimed in claim 1 in which there is an intermediatebonding layer of a nickel aluminum compound between the base member andthe rubbing surface layer.

2. A seal as claimed in claim 1 in which there is an intermediatebonding layer of a nickel aluminum compound between the base member andthe rubbing surface layer.